What did I Buy?

[EdG]

Recently purchased a 1975 Corvette which was in storage for many years due to owner dying in 1978. It is a BBC Block ID 3999289 / Aluminum Intake manifold 3933198 (no date code) / Aluminum Holley Dbl.Pumper no choke horn only ID is 12R10552B (at least 750CFM or 800 CFM) / Rock crusher Muncie Close ratio / If this may help no ID on Heads, Spark plug is Autolite 66 / Hooker chrome sidepipe headers / Strange thing is it has all the bells and whistles AC etc and everything works even the clock! Mother of deceased has had it in storage for over 30 years and she lives outside of Canonsburg Pa. She said he had it rebuilt by Yenko in 1976 or 1977 she wasn't sure. Does anyone have any idea on what this is? All my searches on the internet tells me this has an outside chance of being an LS6 BBC. There are no date codes on anything and only casting numbers I gave above. The engine block had a "125 73" in the casting also, which I believe is a 1974 BBC 454. Emeergency brake was removed to fit the Muncie in it. If anyone can be of assistance I would greatly appreciate it!
The mother never drove it, she kept it as a memorial to her son in a heated garage and had it serviced once in awhile, but finally gave it up to his close friend from college. He never knew she had the car and was in town visiting her, after not seeing her in a very long time. I bought it from him for $30K.....I know I am nuts (at least according to my wife).......